What is the layer of permanently frozen subsoil in the tundra called

If the birth rate of a population of dolphins is 2.0, the death rate is 0.5, and the population size is 100, what is this dolphin's population growth?

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

Photosynthesis uses co2 and cellular respiration produces co2. we call the point when the two processes are in balance--when there is no net production of co2--the compensation point. how might you limit one of the processes in order to achieve a compensation point?